Method of making loom picker from polyvinyl alcohol and product



June 12, 1956 J. w. BAYMILLER 2,750,348

METHOD OF MAKING LOOM PICKER FROM POLYVINYL ALCOHOL AND PRODUCT FiledSept. 9, 1950 awe/WM JOHN W. BAYMILLER METHQD OF MAKING LOOM PICKER FROMPOLYVINYL ALCOHOL AND PRODUCT Applicationseptember 9, 1950, Serial No.184,023

3 Claims. (Cl. 260-43)- This application is a continuation in partof mycopending application Serial No. 717,513, filed'D'ecember 20, 1946, nowabandoned.

This invention relates to loom pick'ersand amethod of making the same.More particularly, the invention relates to an ail-plastic loom pickermolded from a composition comprising a polyvinyl alcohol material whichhas been subjected to elevated temperatures, prior to molding.

Power-operated looms are provided with an automatic mechanism fortossing the shuttle from one side'to the other during the weaving of the:cloth. The mechanism employed comprises a .picker stick that isperiodically thrust in a direction opposite to'the-direction"of'travelof the shuttle so that it engagesthe shuttle atsubstantially the end ofthe path of movement thereof withsuch force as to move it to the otherend of the warp shed.

The shuttle reciprocates 'very rapidly such as 170 to 220 times perminute and, in so doing, engages the picker at the shuttle point with'considerable force. In addition, comparatively large amounts of heat aregenerated through contact of the shuttle point with the picker whichoften causes development of high temperatures in "the body of thepicker.

Heretofore-,-loompickers have been manufactured from such materialsasleather and rubberized fabric. In the case of leather, the servicelife-is extremely short; and in some instances, failureof the picker hasresulted after a period of about two daysuse. Rubberized fabric,generally speaking, is more serviceable than leather, but failuregenerally results after continued. use for a period such as one or twomonths. Proper shuttle action depends largely upon the resiliency of thepicker. For instance, if the picker is hard or nonresilient, the shuttlemay break during operation of the loom. Also, nonresilient pickers tendto project the shuttle too abruptly, causing the shuttle to jerk whichcauses filler yarnpbreakage.

Attempts have been made to provide an all-plastic loom picker which ischaracterized by long service life and by resistance to deteriorationunder the conditions of operation of the loom. However, plastics whichhave been heretofore employed are of such a nature as to fail incomparatively short periods of time because of disintegration of thepicker at elevated temperatures which are developed in high speed loomoperation. This failure is believed to be due to the comparatively lowsoftening points of the plastic material utilized in fabrication of theloom picker.

In order to overcome thisdifiiculty, it has been proposed to shield theplastic by means of resilient metal casings to prevent or delay thedestructive spreading and distortion of the picker resulting fromfrequent contact with the shuttle point. Pickers containing suchresilient metal shields, in additionto being expensive, may fail inservice as a result of a separation of the shield from the pickerbrought about by theextreme conditions of operation caused by continualpoundingof the article by the shuttle point.

nited States Patent "ice It is, accordingly, an object of this inventionto provide a loom picker that can'be manufactured at low cost and whichwill have anunusually long service life.

It is a furtherobject of this invention to provide an allplastic'resilient loom picker characterized by a long service life undertheconditions of operation. of a high speed loom.

Still another object of my invention is the provision of a method 'formaking "an all-plastic resilient loom picker characterized by-longservice life which includes the step of heat treating the moldingcomposition prior to the molding operation.

Another objectqof this invention is the provision of an all-plastic loompicker molded from a particular heat-,

treated polyvinyl alcohol composition containing alkaline earth metalstearates.

These and other objects will become apparent to those skilled in the artupon becoming familiar with the following description.

As disclosed in my above-identified copending application, I.have foundthat loom pickers may be molded from compositions containing-polyvinylalcohol material advantageously plasticized Witha suitable plasticizertherefor. The term polyvinyl alcohol material or its equivalent as-usedherein; is intended to include polyvinyl alcohol and modified polyvinylalcohols of the type described below.

The polyvinyl alcohol employed may be prepared by any method'knowntO'jthCEll't. For'instance, one Widely utilized methodbf preparationcomprises polymerizing vinyl acetate and h'yrolyzing' theresultingpolymer in methyl alcohol. The'resulting polyvinyl alcohol is insolublein methyl alcohol, is precipitated, and separated from the remainingliquid by any suitable means such as filtration.

Representative of the modified polyvinyl alcohols. which areparticularly advantageous for use are the ethylene modified polyvinylalcohols which are polyvinyl alcohols containing ethylene groupsobtained by copolymerizing ethylene and vinyl acetate and removing theacetate groups from the resulting copolymer by hydrolysis;

In accordance with my present. invention I employ a plasticizedpolyvinyl alcohol .material composition containing selected amounts ofalkaline earth metal stearates. Suitable plasticizers which. are foundto be particularly advantageous in the. preparation of the compositionto be molded are the polyhydric alcohols such as glycerine, ethyleneglycol, and the like. In addition to the polyhydric alcohols, otherplasticizers such as aromatic aldehydes, for example benzaldehyde may beemployed. Water itself has been found to be an excellent plasticizer forpolyvinyl alcohol material. However, this particular plasticizer isknown as a fugitive plasticizer in that it is lost by the compositionafter or during molding with the result that a brittle product may beobtained. However, if desired, a plasticizing composition comprisingwater and glycerine may be employed; and during the forming operationthe water is lost by the material, resulting in a product comprisingpolyvinyl alcohol plasticized. with glycerine. Mixtures of the variousplasticizers may be used. For instance, advantageous results maybeobtained from use of a plasticizer comprising benzaldehyde andglycerine.

Examples ofalkaline earth metal stearates are calcium stearate,magnesium stearate, zinc stearate, or their equivalents. Particularlyadvantageous results have been obtained with magnesium stearate. Thealkaline earth metal stearates act to improve toughness and heatresistance in the finished molded picker.

Generally speaking, I have. obtained advantageous results by preparing apicker from a composition comprising about 20 to 65 parts by Weight ofplasticizer for each 100 parts by weight of polyvinyl alcohol and .5 to5 parts by weight of alkaline earth metal stearate for each 100 parts ofpolyvinyl alcohol. Particularly advantageous results have been obtainedutilizing 40 to 50 parts by weight of plasticizer for each 100 parts byweight of polyvinyl alcohol. When less than about 20 parts plasticizerare employed, the resulting molded picker tends to be somewhat brittleand the service life thereof is decreased in that it is less resistantto the shock imparted to it by the rapid motion of the shuttle duringthe loom operation. Also, when the quantity of plasticizer is less than20 parts by weight per 100 parts by weight of polyvinyl alcoholmaterial, a picker of such hardness may result as to cause shuttlebreakage as well as improper shuttle action during loom operation. Whenthe quantity of plasticizer exceeds about 65 parts by weight per 100parts by weight of polyvinyl alcohol, the molded product is somewhatsusceptible to moisture in that the plasticizer absorbs the waterpresent in the surrounding atmosphere; and in those cases wherein thepicker is to be employed in comparatively humid atmosphere, difficultiesare experienced from the presence of moisture in the picker. Inaddition, when the amount of plasticizer exceeds about 65 parts byweight per 100 parts by weight of polyvinyl alcohol, the resultingproduct may be less suitable for use in connection with high-speed loomswherein comparatively high temperatures are developed in the operation.When too much plasticizer is present in the composition, it tends tosoften at elevated temperatures such as those which are encountered inhigh-speed loom operation. Furthermore, the use of more than 65 parts byweight of plasticizer per 100 parts by weight of polyvinyl alcoholmaterial may result in the production of a loom picker which would betoo soft to enable proper shuttle action. As to the stearates, less than.5 part gives no significant improvement whereas more than 5 parts causehandling difiiculties in the manufacture of the material.

When a mixture of plasticizers, such as a glycerinebenzaldehyde mixtureis employed, generally speaking, to 30 parts by weight of each componentof the plasticizer mixture are used per 100 parts by weight of polyvinylalcohol material. Thus the composition may contain polyvinyl alcohol, aplasticizer which is a mixture of benzald ehyde and glycerine, andmagnesium stearate.

In accordance with this invention I have also found that the servicelife of pickers molded from polyvinyl alcohol material is greatlyincreased by the heat treating of the molding composition prior to themolding step. The desired molding composition, as described hereinabove,is first mixed in a suitable mixing device which is advantageously amill; and following mixing, the material is then heated with agitationin air at temperatures of 280 F. to 340 F. The most advantageous meansof accomplishing this heating is that involving milling the mixture on amill while maintaining the temperature within the desired range.Temperatures below 280 F. do not result in the desired improvement inservice life, and temperatures above 340 F. result in decomposition ofthe molding compound. The time of milling may vary depending upon theparticular temperature conditions employed; generally speaking, themilling is continued until the compound is readily separated from themill in the form of a sheet. Ordinarily, this occurs after milling at320 F. to 340 F. for a period of about ten minutes.

Following the heat treating as described above, the molding compound isbroken up in a plastic grindingdevice or micro-pulverizer to obtain apowder which is molded into the shape of a loom picker by any suitablemeans such as compression or injection molding.

My invention may be more readily understood by reference to theaccompanying drawing in which:

Figure l is a side elevation of the finished picker;

Figure 2 is an end elevation of the picker;

Figure 3 is a vertical sectional view on the line III- III; and

Figure 4 is a view illustrating the picker in position on a pickerstick.

An advantageous configuration is that illustrated in the drawing. Asshown, the picker 1 is provided with a channel 2 for receiving thepicker stick and an indentation 3 for engaging the shuttle point duringoperation of the loom.

As illustrated in Figure 4, the picker 1 is attached to the picker stick4 by suitable means such as the screw 5. Generally speaking, it isadvantageous to mold the picker with the channel 2 having across-sectional area substantially equal to but less than thecross-sectional area of the picker stick. ,With such a configuration thepicker is forced onto the picker stick and is partially held in positionduring loom operation by friction.

The loom pickers prepared in accordance with this invention have beensubjected to conditions of high-speed loom operation and have operatedfor periods as high as ten months without failure. A loom pickerprepared in accordance with this invention is not affected by the highhumidity which is generally prevalent in weaving rooms, and this isunusual as polyvinyl alcohol materials are generally accepted as beingsubject to moisture. While I do not intended to be limited by any theoryexpressed herein, it is believed that the heat treatment results inincreased resistance to heat and shock to which the picker is subjectedduring the operation of a loom. Heat treating with mastication in thepresence of air is necessary to increase the heat and shock resistanceas heating in a press or heating by other means does not give theresults desired.

The preparation of a typical composition for the manu facture of pickersis illustrated in the following specific example;

Example Parts by weight Polyvinyl alcohol Glycerine 60 Magnesiumstearate 2 Water 50 Titanium dioxide 5 The titanium dioxide andmagnesium stearate were added to the polyvinyl alcohol and mixed for onehalf hour in a Baker-Perkins mixer. The water was added to the resultingmixture and mixing was continued for one half hour. The resulting masswas allowed to stand overnight, after which the glycerine was slowlyadded and the materials mixed for one half hour. The mixture was allowedto stand overnight, after which it was heat treated on a mill at 330 F.to 340 F. for eight to ten minutes.

I claim:

1. A loom picker made of material comprising polyvinyl alcohol moldedfrom a composition containing polyvinyl alcohol and a metal stearate ofthe group consisting of alkaline earth metal stearates and zinc stearatewhich composition has been heated with mastication in air at atemperature between 280 F. and 340 F. prior to mold- 2. An all-plasticloom picker obtained by forming a molding compound including 100 partsby weight of polyvinyl alcohol, 20 to 65 parts by weight of aplasticizer, and .5 to 5 parts of a metal stearate of the groupconsisting of alkaline earth metal stearates and zinc stearate, heatingsaid molding compound with mastication in air at a temperature between280 F. and 340 F., and molding said heated compound into the shape of aloom picker.

3. A method of making a heat and shock resistant loom picker comprisingforming a molding compound including plasticized polyvinyl alcohol and ametal stearate of the group consisting of alkaline earth metalstearatesand zinc stearate, milling said compound in airata'temperatureapproximately 320 F. to 340 F. for

References Cited in the file of this patent 5 UNITED STATES PATENTS1,932,889 Groff Oct. 31, 1933 2,375,388 Ryan May 8, 1945 2,389,157Kottemann Nov. 20, 1945 10 2,399,401 Sonnichsen et al Apr. 30, 1946 6Nelson Apr. 26, 1949 Swan May 3, 1949 Sadowski July 18, 1950 Porth Oct.30, 1951 Metz June 10, 1952 FOREIGN PATENTS Great Britain May 14, 1934Great Britain May 13, 1947 Canada June 6, 1950

1. A LOOM PICKER MADE OF MATERIAL COMPRISING POLYVINYL ALCOHOL MOLDEDFROM A COMPOSITION CONTAINING POLYVINYL ALCOHOL AND A METAL STEARATE OFTHE GROUP CONSISTING OF ALKALINE EARTH METAL STEARATES AND ZINC STEARATEWHICH COMPOSITION HAS BEEN HEATED WITH MASTICATION IN AIR AT ATEMPERATURE BETWEEN 280* F. AND 340* F. PRIOR TO MOLDING.